Kimmo Kauhaniemi

Synchronized re-connection of island operated LV microgrid back to utility grid

Microgrids can be defined as distribution systems with distributed generation (DG) units, energy storages and controllable loads. Microgrids are expected to form an essential part of future Smart Grids with self-healing feature. Most of the time microgrids will be operated normally parallel with utility grid. In addition to this microgrids have a special self-healing capability, because they can continue operation also in island mode during disturbances, e.g., utility grid outages. One important issue which needs to be solved is the synchronized reconnection of island operated microgrid back to utility grid. In this paper issues related to the re-connection of low voltage (LV) microgrid are studied and different functions to enable synchronized re-connection are presented with various DG unit configurations through simulation studies with PSCAD simulation software.

Fuzzy Models and Techniques for the Calculation of Radial Distribution Networks

Tire fuzzy set tlieory offers au effective way to iiiodel inexact or uncertain data. In this paper it consislent set of fuzzy models and techniques for the calculation of electricity distribution networks is presented. The theories relating to the fuzzy numbers are siruplified into a form suitable for practical application. Also several useful methods of dah representation are given. The utilization of tlie fuzzy approacli is deuioustr:ited by a radial load flow method where the voltage in the substation and the power deuiaucls are represented by fuzzy nuiiibers.

Microgrid voltage level management and role as part of smart grid voltage control

Microgrids can be defined as distribution systems with distributed generation (DG) units, energy storages and controllable loads. Microgrids are expected to form an essential part of future Smart Grids with self-healing feature. Most of the time microgrids will be operated normally parallel with utility grid. In addition to this microgrids have a special self-healing capability, because they can continue operation also in island mode during disturbances, e.g., utility grid outages. Realization of future Smart Grids with island operation capability requires, in addition of solving all technical challenges, also feasible management and market structures to be developed. In this paper LV microgrid voltage level and unbalance management as well as capability to actively participate in Smart Grid voltage control during normal operation has been investigated through studies with PSCAD simulation software.

Microgrid control principles in island mode operation

Microgrids are small power systems capable of island and grid modes of operation. They are based on multiple renewable energy sources that produce electricity. Managing their power balance and stability is a challenging task since they depend on quite a number of variables. This paper reviews microgrid control principles according to the IEC/ISO 62264 standard along with an example system where electricity is supplied by two renewable energy devices including a PV panel, a Doubly-Fed Induction Generator (DFIG) wind turbine and battery storage. The storage system provides the integral system backup and the storage of surplus energy from renewable sources. System simulation is made with PSCAD/EMTDC software.

Secondary control in AC microgrids challenges and solutions

The hierarchical control structure of a microgrid can be described as consisting of four levels: processing, sensing and adjusting, monitoring and supervising, and maintenance and optimizing. This paper focuses on the secondary control level, which can be classified as centralized or decentralized control. A comprehensive investigation of both centralized and decentralized control is presented in this paper. Decentralized control is proposed in order to deal with some of the disadvantages of central control, such as the high risk of unplanned interruption arising from a Microgrid Central Controller (MGCC) malfunction. However, decentralized control is not yet complete, and some challenges to its implementation remain. This paper also looks at these challenges and proposes some solutions that may help to improve the performance of decentralized control and overcome its disadvantages. Finally, a general methodology of microgrid control is modeled.

Power sharing for distributed energy storage systems in AC microgrid: Based on state-of-charge

The approach to optimal control for distributed energy storage systems has been an issue of interest in recent years. In this regard, the performance of power sharing between Energy Storage Units (ESUs) with different States of Charge (SoC) can be enhanced. In this paper, the SoC of each ESU is balanced using the proposed control method, which is decentralized and based on the adaptive droop control method. The droop coefficient should be adjusted in the system on the basis of the SoC of each ESU. With this control strategy, the storage unit with higher SoC provides more power to support the load, while the unit with lower SoC provides the less power. The method is validated using simulation results from PSCAD/EMTDC software.

Integration of distributed energy resources (DER) to the grid

Abstract: This chapter discusses the technical issues of successful integration of distributed energy resources (DER) to the grid. The effects of DER on the power system operation and protection are first identified, and then the technical requirements arising from these effects are introduced. Also the relevant grid codes and standards are discussed.

Wireless Light-Weight IEC 61850 Based Loss of Mains Protection for Smart Grid

Abstract This paper presents a novel Loss of Mains (LoM) protection method based on IEC 61850 Manufacturing Messages Specification (MMS) protocol over wireless Global System for Mobile Communication (GSM) based access point name (APN) mechanism. LoM or anti islanding protection is a key requirement in modern power distribution grids where there is significant amount of distributed energy resources (DER). The future Smart Grids are based on extensive communication capabilities and thus the communication based LoM approaches will also become dominant. The IEC 61850 standard based systems are gaining ground in the substation communication, and therefore, it is natural to expand this technology deeper into the distribution network. Using this standard for LoM protection, also enables some advanced approaches utilizing large variety of information available in the Smart Grid. There is a specific part of the standard, IEC 61850-7-420, which defines logical nodes (LNs) suitable for this purpose; but, there are no available devices applying this part of the standard yet. In this research, a light-weight implementation of IEDs (Intelligent Electronic Devices) is developed using a low-cost open microcontroller platform, Beagle Bone, and an open source software. Using this platform, a wireless LoM solution based on IEC 61850 MMS protocol has been developed and demonstrated. This paper introduces object modelling according to IEC 61850-7-420 defined LNs and an implementation applying direct client server MMS based communication between lightweight IEDs. The performance of the wireless application using the developed platform is demonstrated by measuring the message latencies. In this paper, a novel LoM protection concept is proposed based on the standardized communication solution brought by IEC 61850 and specific LNs for DERs defined in IEC 61850-7-420. A light-weight implementation of an IEC 61850 based IED is developed in order to reduce large overhead information and complexity of the standard. In addition to LoM function, the developed solution has the ability to monitor DERs status. The available monitoring information can be shared among various distribution management systems (DMS), enabling distributed decision approach for various purposes.

Designing and analysis of innovative solutions for harbour area smart grid

Nowadays, different vessel types are mostly operating on diesel generators employing cheap quality fuel, thus causing many types of air pollutions during a stay at the harbour. Thus, electrification by renewable energy based Distributed Generation (DG) and Battery Energy Storage (BES) onboard as well as on shore side are inevitably the best solution to get pollution free energy. In this regard, this paper proposes an innovative design concept of the Harbour Area Smart Grid (HASG) in such a way that it can not only supply the vessels for cold ironing purpose but also supports the hybrid vessels of future technology. The designed HASG is modelled in PSCAD/EMTDC and the simulation case studies have been carried out to validate the performance of the HASG under steady state and transient state.

Evaluation of the hierarchical control of distributed Energy Storage Systems in islanded Microgrids based on Std IEC/ISO 62264

In this paper, a decentralized control methodology based on hierarchical control levels is investigated. In recent years, efforts have been made to develop standards for Microgrids (MGs), and the decentralized control method evaluated here is based on the IEC/ISO 62264 standard. Since the main challenge to decentralized control in Battery Energy Storage Systems (BESSs) is the different levels of stored energy, a modified droop control is used here to share the power between the different storage units, based on the energy level of each unit. The power coefficients of the droop control are set inversely proportionally and directly proportionally, respectively, to the state of charge (SoC) of each battery unit during discharging and charging mode. To evaluate this decentralized method based on the IEC/ISO 62264 standard, PSCAD/EMTDC software is used.